1. Field of the Invention
This invention relates to a diversity receiver for radio communication using digital modulation.
2. Description of the Prior Art
In radio communication between a mobile station and a base station or between mobile stations, a received signal in a reception side tends to undergo fading effects. A diversity reception system is a well-known art for minimizing fading effects by combining at least two received signals or selecting one of at least two received signals.
Generally, in transmission of a radio signal between a mobile station and a base station or between mobile stations, a part of the radio signal directly propagates from a transmitter to a receiver while a remaining part thereof tends to be reflected and scattered by various bodies such as buildings or mountains and then reach the receiver with a delay. Thus, the radio signal propagates from the transmitter to the receiver via multipaths. Accordingly, the signal received by the receiver has a direct signal component and a delay signal component, suffering from a distortion called a multipath distortion. In addition, the received signal tends to undergo frequency selective fading effects caused by multipath propagation.
Generally, it is difficult for a simple or primitive diversity reception system to adequately suppress such frequency selective fading effects.
Some of prior art advanced receivers are designed so as to suppress frequency selective fading effects. As will be described later, such a prior art advanced receiver has some problem.